Percussive tool



July 26, 1927.

F. A. JIMERSON PERCUSSIVE TOOL Filed A112. 26. 1926 INVENTOR flaw/J11 Iii/neuron.

1525 AT ORNEY.

Patented July 26, 1927.

I UNITED STATES PATENT OFFICE.

armors A. .maERsoN, or ArnEns, PENNSYLVANIA, ASSIGNOR 'r'o meERsoLL-Rimn sex sm, or JERSEY crrY, NEW JERSEY, A CORPORATION E NEW JERSEY.

PERCUSSIVE TOOL.

Application filed August 26, 1926. Serial 30.131351.

This invention relates to pneumatic perfront end of t cussive tools and more particularly to that type of hammer tool in which the power is provided by means of a percussive ham- H1811 piston striking against the shank of a too An object of this invention is to auto matically stop'the reciprocatio n of the ham mer piston when the operator fails to bear against the tool. Other objects of the invention will be in part obvious and in part pointed out here inafter. w In the drawing in wh'ichsim'ilar reference characters refer to similar parts, I Figure 1 is a longitudinal section through a'percussive tool constructed in accordance with the practice of'the invention, and

Fi re 2 is a longitudinal section through the ront portion of the tool showing the manner in which the operation of the reciprocation of the hammer piston .is auto matically stopped when pressure on -.-the handle of the tool is released by the operator. Referring to the drawing, the invention is shown embodied in a tool preferably of the type known as coal picks, which are adaptedto be usedas a substitute for hand picks in breaking up masses of coal and similar material. I

The tool comprises a. cylinder A to which a suitable handle B is bolted as by means of a backhead C. Within the cylinder a iston Dis adapted to reciprocate for striking against the shank end E of a tool F inserted in the front head G suitably at-- tached to the end of the cylinder A. The front head G is provided with a bore H, preferably larger than the bore ofthe cyl inder A, into which-the collar J of the shank- E is inserted so as to permit limited longitudinal movement of the tool F with respect to the cylinder A.

The cylinder A is provided with a valve box K having a reciprocating spool valve L folr distribulgiig motigp fluid1 from the su to suita e sup passages P ziiid & lea in to the rear and front ends respectively of t e cylinder A. The motive fluid supply assa e Q. terminates near the lie cylinder in a port R adapted to be overrun slightly by the front en of the reciprocatin of motive fluid m the cylinder A is controlled by the piston D, the spent motive bushing U in order that the shank E only piston D. The exhaust fluid being adapted to pass to atmosphere through centrally located exhaust ports S in the cylinder A. The operation of the valve L to control the distribution of motive fluid to the cylinder A is substantially as described in Patent No. 1,589,295, granted June 15, 1926, to Francis A. J imerson.

It is desirable in operating a tool of this character to hold the tool with force against the work. The tendency is for the shank E to be driven forward out of the path of the piston D in which positionno work is done' and the front head may bedamaged due to the repeated blows of the piston D. This invention provides means for stopping the reciprocation of the piston D when pressure against the handle B is relaxed.

To this end there is provided a plurality of atmospheric exhaust ports T near the end of the cylinder A and. adapted to be controlled by a bushing U ,slidably fitting. in the bore of the cylinder A and fittin snugly around the shank E of .the tool The shank E is slightly longer than the may be struck by the piston D under normal operating conditions. The bushing U is provided with a flanged end V adapted to bear against the collar J by which the bushing is forced in a direction into the cylinder A to. cover the ports T. The diameter of the flange. V is such that it fits substantially the bore H of the front head G.

, During normal operating conditions, the hammer D will strike against the shank E but, due to the pressure against the handle, the tool F and bushing U remain in the position substantially as shown in Fig. 1, wherein the atmo heric ports T are closed 'by the bushing ll. However, if the ressure .against the handle B be relaxed by t e operator, or when for any reason the resistance to the tool is removed as "when a'coal p ck enters a pocket, the piston D W111 hammer the bushing U and the shank E forward to 0 Leakage around the piston into the forward 105 1 s ace is ermitted to pass to atmosphere t rough t e ports T. Means is provided to indicate to the operator that the trouble is not due to a defect in the tool but that he is not providing sufiicient pressure against the handle B. A port W communicating with the bore of the cylinder A from the supply passa e Q and substantially midway 1n the pat of the piston D is adapted to be uncovered by the piston when the latter is allowed to passto the position shown in Figure 2. In the latter position, the port W is uncovered permitting motive fluid to escape through the bore of the cylinder A and out from the exhaust port S. A slight back pressure is produced back of the piston to counteract the tendency of the piston to rebound from the striking face of the shank E. The noise caused by the escape of motive fluid in this manner 1s sufficient to attract the attention of the operator and to indicate that thetrouble is lack of pressure at the handle B permitting the piston D to advance too far forward.

The front head G may be attached to the cylinder A in any suitable manner. In this instance it is internally threaded and is adapted to be secured to the threaded end X of the cylinder A, there being a coil "spring Y interposed between the cylinder and rent head and attached at either end to both said members as shown at the bentover end Z. The tension in the spring Y is suflicient to cause the cylinder and front head to tend to screw together, rather than to unscrew, while it is subjected to the vibration of the tool.

The throttle valve is of the ball type comprising a ball 6 adapted to seat in a passa e c communicating with the supply passage Normally the ball I) is held seated by a coil spring at held in position by means of a plug e into the boss f. The throttle valve is opened by means of a plunger 9' adapted to bear a ainst the ball I) to unseat the latter. The punger g is operated by means of pressure against the handle B which is mounted on a flexible spring-like member it having a free end which may be pressed against the protruding end of the plunger g. A suitable air hose (not showngl may be coupled to the pneumatic tool at t e threaded opening is leading to the supply passage 0 to the space around the ball valve 6.

I claim: I

1. A pneumatic percussive tool comprising a cylinder having motive fluid supply ports communicating with the front and rear ends of said cylinder and centrally disposed exhaust ports, a hammer piston adapted to reciprocate in said cylinder, a front head to receive the shank of a tool to be struck by said hammer piston, means controlled by the shank of said tool to permit escape of motive fluid from the end ofsaid cylinder and a centrally disposed port in said cylinder communicating with one of said supply ports and controlled by said piston to permit the escape of motive fluid back of said piston from one of said ports and to said exhaust port.

2. A pneumatic percussive tool comprising a cylinder having supply passages and ports communicating with oth ends of said cylinder, and centrally disposed exhaust ports, a hammer piston adapted to reciprocate in said cylinder, a front head for said cylinder, a bushing in said front head slidable in said cylinder and adapted to receive the shank of a tool to be struck by said piston, atmospheric exhaust ports in said cylinder controlled by said bushing, and a port in said cylinder communicating with one of said supply passages and uncovered by said piston when moved forwardly beyond its normal stroke.

In testimony whereof I have signed this specification.

FRANCIS A. JIMERSON. 

